When it debuted in early 1981, this series, about a police precinct in an unnamed American city, couldn’t get arrested in the ratings. It mixed street crime with precinct politics and issues between commanders and “blues” (uniformed police officers). However, when Rene Enrique (who portrayed second in command Lt. Ray Calletano) visited San Francisco that year, he told me: “I credit The Chronicle with helping to get the show renewed for a second season with its coverage. ... NBC realized it had to examine its conscience. ... (You) critics saved the show.” Producer Steve Bochco would keep it alive for seven seasons, and this fourth time out (22 episodes on four discs) reflects a unique mixture of “M*A*S*H” and “Law & Order” in focusing on dozens of central characters and their interwined relationships. Plus all those weirdos, sleazy types and gang members roaming the streets. Notable about this season is that Michael Conrad, who portrayed the officer who introduced each show with a comedic morning briefing that ended with “And hey ... let’s be careful out there,” died while filming an episode in November 1983. This makes “Grace Under Pressure” (on disc four) a must-see dedication to his memory. The top-ranking cop, Capt. Furillo (Daniel J. Travanti), usually bore the brunt of disagreements among the headquarters staff. Dozens of subplots and relationships (Charles Haid, Joe Spano, Michael Warren, James Sikking, Betty Thomas) fill each show to the max. Ironically, the show that was about to die went on to win four Emmys. — John Stanley